Users of Phazon-Enhancement Devices ( Metroid Prime 3: Corruption).Mega Man ( Mega Man 11) via Double Gear system.Users of the "Eyes of Etro" ( Final Fantasy XIII-2).Non-Belmont users of the Vampire Killer ( Castlevania).Asura ( Asura's Wrath) via his Wrath Form.Sam Winchester ( Supernatural) via Demon Blood.Users of the Mark of Cain ( Supernatural).Cordelia Chase ( Buffy the Vampire Slayer/Angel).Willow Rosenberg ( Buffy the Vampire Slayer).Caleb ( The Covenant) after his ascension.The Five Family Members ( The Covenant).Bagi ( Bagi, the Monster of Mighty Nature).Spirit Users ( Vampire Academy/Bloodlines).Mundanes ( Shadowhunter Chronicles) via Lilith's blood.
Dark Wizards ( Harry Potter) especially when creating Horcruxes.Eli Shane ( Slugterra) using the double barrel with the wrong slugs for a fusion shot could cause disastrous results like draining all the energy of surrounding slugs or worse.Kenny McCormick/Mysterion ( South Park) cannot die but can still feel pain.Zombie Spider-Man ( Marvel Comics) using his own veins and arteries as webbing causes him intense pain.Wielders of the Ebony Blade ( Marvel Comics).Guido Carosella/Strong Guy ( Marvel Comics).Mar-Vell/Captain Marvel ( Marvel Comics) is kept alive and given powers by his Nega-Bands, but they prevent him from being treated when he is diagnosed with Blackend (cancer).Some Akumatized villains ( Miraculous: Tales of Ladybug & Cat Noir).Miraculous holders ( Miraculous: Tales of Ladybug & Cat Noir).Spark ( Girl Genius) there's a reason it's called The madness place.Clark Kent/Kal-El/Superman ( DC Comics) via Solar Flare, later Kryptonite energy infusion.Speedsters ( DC Comics) via Speed Force.Darkwing Duck ( Darkwing Duck) via former use of Super Speed powers.Danny Fenton/Phantom ( Danny Phantom) formerly.Avatars ( Avatar: The Last Airbender) via the Avatar State.Anne Boonchuy ( Amphibia) via her Calamity powers.
Some double-edged powers may affect people other than the user.Overuse or misuse of said power may result in, among other things, insanity and physical damage to the user's body. The user possesses great skill and power, but prolonged usage of it may come at a cost.